Use of buffer occupancy as a basis to control configuration of dual-connectivity service

ABSTRACT

When a first node is considering setup of dual-connectivity service for a UE, the first node will take into consideration data-buffer occupancy of one or more candidate second nodes, in order to decide whether to set up the dual-connectivity service for the UE and/or to decide which of multiple second nodes to use for the UE&#39;s dual-connectivity service. For instance, if a candidate second node has threshold high data-buffer occupancy, then, based on that fact, the first node may decide to not use that second node for dual-connectivity service of the UE. Or the first node may decide to use a given candidate second node based on the given candidate second node having lower data-buffer occupancy than one or more other candidate second nodes. Further, data-buffer occupancy could be based on downlink data buffering and/or uplink data buffering.

BACKGROUND

A cellular wireless network typically includes a number of base stationsthat are configured to provide wireless coverage areas in which userequipment devices (UEs) such as cell phones, tablet computers,machine-type-communication devices, tracking devices, embedded wirelessmodules, and/or other wirelessly equipped communication devices (whetheror not user operated) can operate. Each base station could be coupledwith a core network that provides connectivity with various applicationservers and/or transport networks, such as the public switched telephonenetwork (PSTN) and/or the Internet for instance. With this arrangement,a UE within coverage of the cellular network could engage in airinterface communication with a base station and could therebycommunicate via the base station with various application servers andother entities.

Such a network could operate in accordance with a particular radioaccess technology (RAT), with communications from the base stations toUEs defining a downlink or forward link and communications from the UEsto the base stations defining an uplink or reverse link.

Over the years, the industry has embraced various generations of RATs,in a continuous effort to increase available data rate and quality ofservice for end users. These generations have ranged from “1G,” whichused simple analog frequency modulation to facilitate basic voice-callservice, to “4G”—such as Long Term Evolution (LTE), which nowfacilitates mobile broadband service using technologies such asorthogonal frequency division multiplexing (OFDM) and multiple inputmultiple output (MIMO). And most recently, the industry is now exploringdevelopments in “5G” and particularly “5G NR” (5G New Radio), which mayuse a scalable OFDM air interface, advanced channel coding, massiveMIMO, beamforming, and/or other features, to support higher data ratesand countless applications, such as mission-critical services, enhancedmobile broadband, and massive Internet of Things (IoT).

In accordance with the RAT, each coverage area could operate on one ormore radio-frequency (RF) carriers, each of which could be frequencydivision duplex (FDD), defining separate frequency channels for downlinkand uplink communication, or time division duplex (TDD), with a singlefrequency channel multiplexed over time between downlink and uplink use.

Further, on the downlink and uplink, each carrier could be structured todefine various physical channels including time-frequency resources forcarrying information between the base station and UEs. For example, theair interface could be divided over time into frames, each divided inturn into subframes and timeslots, and the carrier bandwidth (frequencywidth of the carrier on the downlink and/or uplink) could be dividedover frequency into subcarriers, which could be grouped within eachsubframe and timeslot to define physical resource blocks (PRBs) in whichthe subcarriers can be modulated to carry data.

In addition, certain resources on the downlink and/or uplink of eachsuch carrier could be reserved for special purposes. For instance, onthe downlink, certain resources could be reserved to define a referencesignal that UEs could measure in order to determine coverage strength,other resources could be reserved to carry downlink control-planesignaling from the base station to UEs, and other resources could bereserved to carry user-plane communications from the base station toUEs. And on the uplink, certain resources could be reserved to carryuplink control-plane signaling from UEs to the base station, and otherresources could be reserved to carry user-plane communications from UEsto the base station.

OVERVIEW

In example operation, when a UE enters into coverage of such a network,the UE could initially scan for and detect threshold strong coverage ofa base station on a carrier, and the UE could responsively engagesignaling with the base station to establish a Radio Resource Control(RRC) connection between the UE and the base station. Further, ifappropriate, the UE could then engage in attach signaling with acore-network controller to attach and thus register for service, and thecore-network controller could coordinate setup for the UE of one or moreuser-plane bearers, each including an access-bearer portion that extendsbetween the base station and a core-network gateway that providesconnectivity with a transport network and a data-radio-bearer portionthat extends over the air between the base station and the UE.

Once the UE is connected and attached, the base station could then servethe UE with packet-data communications.

For instance, when the core-network gateway receives user-plane data fortransmission to the UE, the data could flow to the base station, and thebase station could buffer the data, pending transmission of the data tothe UE. With the example air-interface configuration noted above, thebase station could then allocate downlink PRBs in an upcoming subframefor carrying at least some of the data to the UE. And in that subframe,the base station could transmit to the UE a scheduling directive thatindicates which PRBs will carry the data, and the base station couldtransmit the data to the UE in those PRBs.

Likewise, on the uplink, when the UE has user-plane data fortransmission on the transport network, the UE could buffer the data,pending transmission of the data to the base station, and the UE couldtransmit to the base station a scheduling request that carries a bufferstatus report (BSR) indicating the quantity of data that the UE hasbuffered for transmission. With the example air-interface configurationnoted above, the base station could then allocate uplink PRBs in anupcoming subframe to carry at least some of the data from the UE andcould transmit to the UE a scheduling directive indicating thoseupcoming PRBs, and the UE could accordingly transmit the data to thebase station in those PRBs.

For both downlink and uplink, depending on PRB availability, the basestation may schedule transmission of just some of the buffered data at atime. For instance, when the base station has a set of data buffered fortransmission to the UE, the base station may schedule and engage intransmission of just some of that data in one subframe and then scheduleand engage in transmission of more of the data in a subsequent subframe,and so forth. And when the UE has a set of data buffered fortransmission to the base station, the base station may schedule, and theUE may engage in, transmission of just some of that data in one subframeand then the base station may schedule, and the UE may engage in,transmission of more of the data in a subsequent subframe, and so forth.

As the industry advances from one generation of RAT to the next, issuesarise with the need for UEs to support potentially multiple RATs atonce. With the transition from 4G LTE to 5G NR, for instance, it isexpected that networks and UEs will be configured to support use of bothtechnologies concurrently, with an arrangement referred to as EUTRA-NRDual Connectivity (EN-DC). With such an arrangement, a UE might includea 4G radio and a 5G radio, and the 4G radio could be served by a 4G basestation concurrently with the 5G radio being served by a 5G basestation. This arrangement could help support transition from 4Gtechnology to 5G technology and could also facilitate higher peak datarate of communication by allowing data to be multiplexed over 4G and 5Gconnections, among possibly other benefits.

More generally, dual connectivity could encompass connectivity on two ormore RATs concurrently, to facilitate technology transitions or forother purposes. Dual-connectivity can thus be distinguished fromstandalone connectivity, where a UE is served on just one RAT, such asjust LTE for instance.

In some dual-connectivity arrangements, one base station operating undera first RAT could serve as a master node (MN), responsible forcoordinating setup and teardown of dual-connectivity service for a UEand for handling core-network control-plane signaling related to thedual-connectivity service, and another base station operating under asecond RAT could serve as a secondary node (SN) to provide increaseddata capacity for the UE. For example, with EN-DC, a 4G base station(e.g., an evolved Node-B (eNB)) could operate as the MN, and a 5G NRbase station (e.g., a next generation Node-B (gNB)) could operate as theSN.

Further, in an example of such an arrangement, one of the UE's twoconnections might be used for both downlink and uplink communication,while the other connection might be used for just downlinkcommunication. In an example EN-DC implementation, for instance, where anetwork's 4G capacity may be more limited than its 5G capacity, a UE's5G connection could be used for both downlink and uplink service, butthe UE's 4G connection may be used for just downlink service. Otherimplementations are possible as well, however.

When the UE enters into coverage of such a system, the UE couldinitially scan for and discover threshold strong coverage of the MNunder a first RAT (e.g., 4G coverage, for EN-DC), and the UE couldresponsively engage in signaling as discussed above to establish an RRCconnection between the UE and the MN. Further, the UE could engage inattach signaling with a core-network controller via the MN, and thecore-network controller could coordinate establishment for the UE of atleast one bearer as discussed above.

The MN could then serve the UE in a standalone mode with packet-datacommunications in the manner described above. Further, the MN couldtrigger and/or engage in a process to establish for the UE a secondaryRRC connection with an SN, so that the MN and SN can then cooperativelyprovide the UE with dual-connectivity service.

For instance, the MN could direct the UE to scan for secondary coverageunder the second RAT and could receive in response from the UE a reportthat the UE detected threshold strong coverage of one or more SNs. Andthe MN could then coordinate setup of dual-connectivity service with theUE being served by the MN and such an SN.

While the specifics of setting up dual-connectivity may vary fromimplementation to implementation, in an example, the MN could engage insignaling with the SN, with the UE, and with the core-networkcontroller, to coordinate setup of the dual-connectivity service. Forinstance, the MN could engage in signaling with the UE and with the SNto coordinate setup of a secondary connection between the UE and the SN.And the MN could engage in signaling with the core-network controllerand/or with the SN to coordinate setup of a split bearer for the UE sothat the MN could serve a portion of the UE's data communications andthe SN could serve another portion of the UE's data communications.

Further, various split-bearer arrangements may be possible.

In one implementation, the split bearer could be established at thegateway, with one bearer leg extending between the gateway and the MNand another bearer leg extending between the gateway and the SN. Forinstance, while maintaining the UE's access-bearer between the MN andthe gateway, the core-network controller could coordinate setup of asecondary access bearer between the SN and the gateway. With thisarrangement, communications between the UE and the MN could flow overthe access bearer between the MN and the gateway, and communicationsbetween the UE and the SN could flow over the access bearer between theSN and the gateway.

In another implementation, the split bearer could be established at theSN, with the UE's access bearer extending between the gateway and the SNand a leg of the bearer extending further between the SN and the MN. Forinstance, the core-network controller could coordinate transfer of theUE's access bearer from being between the gateway and the MN to insteadbeing between the gateway and the SN, and the MN and SN could coordinatesetup of the bearer leg between the MN and the SN. With thisarrangement, communications between the SN and the UE would flow overthe access bearer between the SN and the gateway, and communicationsbetween the MN and the UE would flow between the MN and the SN andlikewise over the access bearer between the SN and the gateway.

And in yet another implementation, the split bearer could be establishedat the MN, with the UE's access bearer still extending between thegateway and the MN, and with a leg of the bearer extending between theMN and the SN. For instance, the MN could maintain the access bearerbetween the MN and the gateway, and the MN and SN could coordinate setupof the bearer leg between the MN and the SN. With this arrangement,communications between the MN and the UE could flow over the accessbearer between the MN and the gateway, and communications between the SNand the UE could flow between the SN and the MN and likewise over theaccess bearer between the MN and the gateway.

Other split-bearer arrangements might be possible as well.

With dual-connectivity service so established through this and/or othersteps, the MN and SN could then concurrently serve the UE over theirrespective connections with the UE, perhaps with both providing for bothdownlink and uplink downlink scheduled data communication, or perhapswith both providing for downlink scheduled data communication but justone of them providing for uplink scheduled data communication.

On the downlink, for instance, some of the data destined to the UE couldbe buffered by the MN for transmission to the UE, and the MN couldcoordinate downlink transmission of data over the air from the MN to theUE as discussed above. And other of the data destined to the UE could bebuffered by the SN for transmission to the UE, and the SN couldcoordinate downlink transmission of that data over the air from the SNto the UE as discussed above.

Likewise, when the UE has data to transmit, the UE could buffer some ofthat data for transmission to the MN as discussed above and the UE couldbuffer other of that data for transmission to the SN as discussed above.Thus, the UE could send to the MN a BSR indicating how much data the UEhas buffered for transmission to the MN, and the MN could coordinateuplink transmission of that data over the air from the UE to the MN. Andthe UE could send to the SN a BSR indicating how much data the UE hasbuffered for transmission to the SN, and the SN could coordinate uplinktransmission of that data over the air from the UE to the SN.Alternatively, the UE could limit its uplink transmission to just theSN.

One technical problem that can arise in this process stems from the factthat an SN that the MN decides to configure for use in dual-connectivityservice of a UE will have limited resources. Even if the SN operates onone or more relatively wide-bandwidth carriers, the SN may handle agreat extent of data communication over its air interface at any giventime, perhaps for multiple UEs at once. As a result, there could bedelays in scheduling communication of buffered data over the SN's airinterface to and from each UE served by the SN. Ultimately, these delaysand the associated buffer fullness may impact user experience and/orgive rise to other issues.

The present disclosure provides an improvement to help address thisproblem.

In accordance with the disclosure, when an MN is considering setup ofdual-connectivity service for a UE, the MN will take into considerationthe data-buffer occupancy of one or more potential (candidate) SNs, inorder to decide whether to set up the dual-connectivity service for theUE and/or to decide which of multiple SNs to use as an SN for the UE'sdual-connectivity service. For instance, if a candidate SN has thresholdhigh data-buffer occupancy, then, based on that fact, the MN may decideto not use that SN for dual-connectivity service of the UE. Or if afirst candidate SN has lower data-buffer occupancy than a secondcandidate SN, then, based on that fact, the MN may decide to use thefirst SN rather than the second SN for dual-connectivity service of theUE.

In this process, the MN could take into consideration an SN's downlinkdata-buffer occupancy, such as a total quantity of data that the SN hasbuffered for transmission to one or more UEs. Alternatively oradditionally, the MN could take into consideration an SN's uplinkdata-buffer occupancy, such as a total quantity of data that the one ormore UEs served by the SN have buffered for transmission to the SN.Further, the MN could consider statistical measures of these bufferoccupancies per SN, such as averages per unit time over a recent slidingwindow, or the like, and the MN could further consider historical trendsregarding such buffer occupancy per SN, such as on a time-of-day basisfor instance.

These as well as other aspects, advantages, and alternatives will becomeapparent to those reading the following description, with referencewhere appropriate to the accompanying drawings. Further, it should beunderstood that the discussion in this overview and elsewhere in thisdocument is provided by way of example only and that numerous variationsare possible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of an example network arrangementin which features of the present disclosure can be implemented.

FIG. 2 is a flow chart depicting an example method in accordance withthe present disclosure.

FIG. 3 is another flow chart depicting an example method in accordancewith the present disclosure.

FIG. 4 is a simplified block diagram of an example base station operablein accordance with the present disclosure.

DETAILED DESCRIPTION

An example implementation will now be described in the context of EN-DCservice. In particular, the example implementation will be described inthe context a network that provides coverage on both 4G LTE and 5G NR,and where at least some UEs served by the network are EN-DC capable. Itshould be understood, however, that the principles disclosed hereincould extend to apply in other scenarios as well, such as with respectto other RATs. Further, variations from the specific arrangements andprocesses described are possible. For instance, various describedentities, connections, functions, and other elements could be added,omitted, distributed, re-located, re-ordered, combined, or changed inother ways.

FIG. 1 depicts an example network having a 4G base station (e.g., eNB)12 that is configured to provide 4G service on one or more 4G carriers14, and at least two example 5G base stations 16, 18 (e.g., gNBs), eachconfigured to provide 5G service on one or more 5G carriers 20, 22.These base stations could be collocated with each other and couldprovide coverage in largely the same direction as each other, to definean area in which UEs can engage in both 4G service provided by the 4Gbase station 12 and 5G service provided by a 5G base station 16, 18.

In representative 4G and 5G implementations, each carrier could be FDDor TDD and could thus define separate downlink and uplink frequencychannels or a single frequency channel multiplexed over time betweendownlink and uplink use. In any event, each frequency channel of acarrier could be characterized by a defined frequency bandwidth (widthin RF spectrum) and center frequency and may have a unique carrieridentifier.

Further, the air interface on each carrier could be structured asdescribed above by way of example, being divided over time into frames,subframes, timeslots, and symbol time segments, and over frequency intosubcarriers, thus defining an array of air-interface resource elementsgrouped into PRBs allocable by the base station for use to carry data toor from served UEs. Carrier-structure and/or service on the 4G and 5Gair-interfaces, however, could differ from each other in various waysnow known or later developed, such as with one implementing variablesubcarrier spacing and the other having fixed subcarrier spacing, withone having flexible TDD configuration and the other having fixed TDDconfiguration, with one having different symbol time segments than theother, and/or with one making different use of MIMO technologies thanthe other, among other possibilities.

As further shown, the example 4G and 5G base stations the examplearrangement are each connected with a core network 24, such as anEvolved Packet Core (EPC) network or Next Generation Core (NGC) network.In the example shown, the core network includes a serving gateway (SGW)26, a packet data network gateway (PGW) 28, and a mobility managemententity (MME) 30, though other arrangements are possible as well.

In an example implementation, without limitation, each base stationcould have an interface with the SGW, the SGW could have an interfacewith the PGW, and the PGW could provide connectivity with a transportnetwork 32. Further, each base station could have an interface with theMME, and the MME could have an interface with the SGW, so that the MMEcould coordinate setup of bearers for UEs to enable the UEs to engage inpacket-data communication via 4G and 5G. Alternatively, just the 4G basestation might have an interface with the MME and may function as ananchor for signaling with the MME both for 4G service and for 5G andEN-DC service.

FIG. 1 further depicts example UEs 34 that may be within coverage of the4G and 5G base stations and may be served by the base stations. In arepresentative implementation, all of these example UEs are 5G capable,such as by including a 5G radio and associated equipment and logic thatenables the UEs to connect with and be served by a 5G base station. Ofthose UEs, some might be configured to directly connect with a 5G basestation and engage in 5G service without regard to 4G service, andothers might be configured to engage in EN-DC service, where theyconnect first with the 4G base station and then establish secondaryconnection with a 5G base station. In either case, from time to time, 5Gbase stations 16, 18 may each provide various UEs with 5G communicationservice. Further, in an example implementation, this 5G service mayinclude both downlink 5G service and uplink 5G service.

A UE that is configured to directly connect with and be served by a 5Gbase station without regard to 4G service may, upon entering intocoverage of the base stations, initially scan for 5G coverage anddiscover threshold strong coverage of one of the 5G base stations on a5G carrier. The UE may then engage in RRC signaling with that 5G basestation to establish a 5G RRC connection on the 5G carrier as discussedabove. Further, if appropriate, the UE may engage in attach signalingwith the MME through the 5G RRC connection, and the MME may coordinatesetup of a bearer for the UE. The 5G base station may then serve the UEwith packet-data communications over the UE's 5G connection in themanner discussed above.

A UE that is configured to engage in EN-DC service, on the other hand,may, upon entering into coverage of the base stations, initially scanfor 4G coverage and discover threshold strong coverage of 4G basestation 12 on a 4G carrier. The UE may then engage in RRC signaling withthat 4G base station to establish a 4G RRC connection on the 4G carrieras discussed above. And if appropriate, the UE may engage in attachsignaling with the MME through the 4G RRC connection, and the MME maycoordinate setup of a bearer for the UE. Further, the 4G base stationcould then select a 5G base station to provide secondary connectivityfor the UE, and the 4G base station could coordinate setup of EN-DCservice for the UE, including setup for the UE of a 5G connection withthe 5G base station on a 5G carrier, and setup of a split bearer asdiscussed above. The 4G base station and 5G base station could then eachserve the UE with packet-data communications over their respectiveconnection with the UE, in the manner discussed above.

In line with the discussion above, the 4G base station could take intoaccount buffer occupancy of one or more candidate 5G base stations inorder to decide whether to set up EN-DC service for the UE and/or inorder to decide which of multiple 5G base stations to use as an SN forthe UE's EN-DC service.

In a representative implementation, the 4G base station could firstidentify a candidate set of one or more candidate 5G base stationsavailable for possible use in EN-DC service of the UE. The 4G basestation could be pre-provisioned with data indicating this candidateset, perhaps one or more 5G base station that provide coveragecollocated with coverage of the 4G base station. Or the 4G base stationcould direct the UE to scan for 5G coverage and could receive inresponse from the UE a report indicating that the UE has detectedthreshold strong coverage of each of one or more such 5G base stationsdefining the candidate set. In the arrangement of FIG. 1, the candidateset might be 5G base stations 16, 18. Or the candidate set might be justone of those 5G base stations. In another arrangement, the candidate setmay include one or more other 5G base stations, perhaps more than two.

The 4G base station could then decide, based on buffer occupancy of each5G base station of the candidate set, whether to set up EN-DC servicefor the UE. For instance, the 4G base station could determine whetherbuffer occupancy of each 5G base station of the candidate set is greaterthan a predefined threshold (e.g., a threshold set by engineering designas being unduly high). If the 4G base station thus determines thatbuffer occupancy of each 5G base station of the candidate set is greaterthan the predefined threshold, then, based on that determination, the 4Gbase station could decide to not set up EN-DC service for the UE.Whereas if the 4G base station thus determines that buffer occupancy ofat least one 5G base station of the candidate set is not greater thanthe predefined threshold, then, based on that determination, the 4G basestation could decide to set up EN-DC service for the UE. The 4G basestation could then proceed accordingly.

Further, if there are at least two 5G base stations in the candidateset, the 4G base station could use buffer occupancy per 5G base stationas a basis to select a 5G base station from among those in the candidateset to be an SN for the UE's EN-DC service. For instance, the 4G basestation could compare the buffer occupancy of the candidate 5G basestations (perhaps candidate 5G base stations each deemed to have nogreater than the threshold level of buffer occupancy), and the 4G basestation could select one of the 5G base stations to be an SN for theUE's EN-DC service, with the selecting being based on a determination bythe 4G base station that the selected 5G base station has lower bufferoccupancy than each other 5G base station of the candidate set. The 4Gbase station could then coordinate setup of EN-DC service for the UE,including setup of a 5G connection between the UE and the selected 5Gbase station, and setup of a split bearer, as discussed above.

To facilitate this process, the 4G base station could have access to andrefer to buffer-occupancy data that indicates the buffer occupancyrespectively for each of various 5G base stations. Each such 5G basestation may regularly report its respective buffer occupancy to the 4Gbase station for storage as part of this buffer-occupancy data and/ormay report its respective buffer occupancy to another entity, such as anelement management system (EMS) server that the 4G base station couldquery, among other possibilities. Further, as noted above, the bufferoccupancy per 5G base station could relate to downlink buffering and/oruplink buffering.

As to the downlink, the buffer occupancy of a 5G base station could be ameasure of quantity of data buffered for transmission by the 5G basestation to one or more UEs connected with the 5G base station. Thiscould be a count of bytes of such data buffered for all such UEsconnected with the 5G base station and/or a percentage of a maximumbuffer capacity occupied with such buffered data, among otherpossibilities. Further, the downlink buffer occupancy of a 5G basestation could be a statistical measure of such buffer occupancy, such asan average over a sliding window of time. And the downlink bufferoccupancy could be current data (e.g., over a most recent ormost-recently reported sliding window of time) or could be historicaldata, such as a rolled up average of such occupancy per time of day orthe like.

As to the uplink, the buffer occupancy of a 5G base station could be ameasure of quantity of data buffered by one or more UEs connected withthe 5G base station, for transmission to the 5G base station. The 5Gbase station could determine this information based on the buffer statusreports that it receives from connected UEs. Similar to downlink bufferoccupancy, the uplink buffer occupancy could represent a count of bytesof such data buffered by all such UEs connected with the 5G base stationand/or a percentage of maximum buffer occupancy of such UEs, among otherpossibilities. Further, the uplink buffer occupancy could represent astatistical measure of such buffer occupancy, such as an average over asliding window of time. And the uplink buffer occupancy could likewisebe current data (e.g., over a most recent or most-recently reportedsliding window of time) or could be historical data, such as a rolled upaverage of such occupancy per time of day or the like.

Further, the buffer-occupancy data could include a consolidatedrepresentation of buffer occupancy per 5G base station, such as a rolledup average or other statistical measure based on the 5G base station'sdownlink and uplink buffer occupancy. Or the 4G base station couldevaluate the buffer-occupancy data to generate such a measure percandidate 5G base station.

The 4G base station could thus refer to the buffer-occupancy data todetermine for each 5G base station of the candidate set whether thebuffer occupancy of the 5G base station is predefined threshold high.This could involve determining if the 5G base station's actual/currentbuffer occupancy is threshold high. Alternative or additionally, thiscould involve predicting, based on historical uplink-noise data, whetherthe 5G base station's buffer-occupancy is now or is about to bethreshold high—such as by determining that the 5G base station tends tohave threshold high buffer occupancy at the current time of day. Asnoted above, based on this analysis, the 4G base station could thusdecide whether to set up EN-DC service for the UE.

Further, the 4G base station could refer to the buffer-occupancy data tosimilarly determine the buffer-occupancy of each of multiple 5G basestations in a candidate set, likewise as an actual measure or apredicted measure. And the 4G base station could select a 5G basestation from the candidate based on the selected 5G base station havinglower determined buffer occupancy than each other 5G base station of thecandidate set. The 4G base station could then set up EN-DC service forthe UE with respect to the selected 5G base station, includingcoordinating setup of a 5G connection between the UE and the selected 5Gbase station and coordinating setup of a split bearer for the UE.

Note that the buffer occupancy per 5G base station may thus be based ondata buffered to and/or from one or more UEs currently connected withthe 5G base station or that were connected with the 5G base station inthe past. Some or all such UE connections could be directly with the 5Gbase station without regard to 4G service. Further, some or all such UEconnections could be secondary connections with the 5G base station forEN-DC service, among other possibilities.

Note also that buffer occupancy could be one of possibly multiplefactors considered by the 4G base station in deciding whether to set upEN-DC service for the UE and/or deciding which of multiple candidate 5Gbase stations to use as an SN for EN-DC service of the UE. The 4G basestation might also take into account other, additional factors, such asreported signal strength, transmission power, noise level, resourceusage, and/or the like.

FIG. 2 is next a flow chart depicting an example method for controllingconfiguration of dual-connectivity service for a UE, thedual-connectivity service including the UE being served concurrentlyover a first connection according to a first RAT and over a secondconnection according to a second RAT. In an example implementation, thefirst RAT could be 4G LTE, the second RAT could be 5G NR, and thedual-connectivity service could be EN-DC. Further, the method could becarried out in a wireless communication system such as that shown inFIG. 1, including a first base station configured to provide serviceaccording to the first RAT and a second base station configured toprovide service according to a second RAT.

As shown in FIG. 2, at block 36, the method includes, while the UE has afirst connection with a first base station according to the first RAT,the first base station determining a buffer occupancy of a candidatesecond base station. At block 38, the method then includes the firstbase station using the determined buffer occupancy of the candidatesecond base station as a basis to make a decision of whether toconfigure dual-connectivity service for the UE in which the UE is servedconcurrently over the first connection with the first base stationaccording to the first RAT and over a second connection with thecandidate second base station according to the second RAT. And at block40, the method includes the first base station controlling configurationof the dual-connectivity service for the UE in accordance with thedecision.

In line with the discussion above, the buffer occupancy in this methodcould comprise a measure that is based on downlink buffer occupancyand/or uplink buffer occupancy. The downlink buffer occupancy could bebased on user-plane data buffered by the second base station pendingtransmission to one or more UEs connected with the second base station.And the uplink buffer occupancy could be based on user-plane databuffered by one or more UEs connected with the second base stationpending transmission to the second base station. In addition, the act ofdetermining the buffer occupancy of the candidate second base stationcould involve receiving from the candidate second base station a reportof the buffer occupancy.

Further, as discussed above, the act of using the determined bufferoccupancy of the candidate second base station as a basis to make thedecision of whether to configure the dual-connectivity service with theUE having the second connection with the candidate second base stationcould involve (a) making a determination of whether the determinedbuffer occupancy of the candidate second base station is at leastpredefined threshold high, (b) if the determination is that thedetermined buffer occupancy of the candidate second base station is atleast predefined threshold high, then, based at least on thedetermination, deciding to not configure the dual-connectivity servicewith the UE having the second connection with the candidate second basestation, and (c) if the determination is that the determined bufferoccupancy of the candidate second base station is not at leastpredefined threshold high, then, based at least on the determination,deciding to configure the dual-connectivity service with the UE havingthe second connection with the candidate second base station.

Still further, as discussed above, the act of using the determinedbuffer occupancy of the candidate second base station as a basis to makethe decision of whether to configure the dual-connectivity service withthe UE having the second connection with the candidate second basestation could involve (a) making a determination of whether thedetermined buffer occupancy of the candidate second base station isgreater than a determined buffer occupancy of another candidate basestation, (b) if the determination is that the determined bufferoccupancy of the candidate second base station is greater than thedetermined buffer occupancy of the other candidate base station, then,based at least on the determination, deciding to not configure thedual-connectivity service with the UE having the second connection withthe candidate second base station, and (c) if the determination is thatthe determined buffer occupancy of the candidate second base station isnot greater than the determined buffer occupancy of the other candidatebase station, then, based at least on the determination, deciding toconfigure the dual-connectivity service with the UE having the secondconnection with the candidate second base station.

In addition, as discussed above, if the determination is that thedetermined buffer occupancy of the candidate second base station isgreater than the determined buffer occupancy of the other candidate basestation, then the method could involve, based at least on thedetermination, configuring the dual-connectivity service with the UEhaving the second connection with the other candidate base stationinstead of with the candidate second base station.

Yet further, as discussed above, the act of controlling configuration ofthe dual-connectivity service for the UE in accordance with the decisioncould involve (a) if the decision is to configure the dual-connectivityservice with the UE having the second connection with the candidatesecond base station, then engaging by the first base station insignaling to configure the dual-connectivity service with the UE havingthe second connection with the candidate second base station, and (b) ifthe decision is to not configure the dual-connectivity service with theUE having the second connection with the candidate second base station,then not engaging by the first base station in the signaling toconfigure the dual-connectivity service with the UE having the secondconnection with the candidate second base station. Here, configuring thedual-connectivity could include triggering, coordinating, managing, orotherwise facilitating the dual-connectivity.

Note that while the above discussed features could be carried out by thefirst base station (e.g., by a 4G base station in EN-DC), the featurescould alternatively be carried out by one or more other entities, suchas by the MME or an EMS, among other possibilities. FIG. 3 is anotherflow chart depicting a method like that discussed above with respect toFIG. 2, but where the operations could be carried out by the first basestation and/or by one or more other entities.

As shown in FIG. 3, at block 42, the method includes, while the UE has afirst connection with a first base station according to the first RAT,determining a buffer occupancy of a candidate second base station. Atblock 44, the method then includes using the determined buffer occupancyof the candidate second base station as a basis to make a decision ofwhether to configure dual-connectivity service for the UE in which theUE is served concurrently over the first connection with the first basestation according to the first RAT and over a second connection with thecandidate second base station according to the second RAT. And at block46, the method includes controlling configuration of thedual-connectivity service for the UE in accordance with the decision.

Various features described above can be implemented in this context, andvice versa.

FIG. 4 is next a simplified block diagram of depicting an example basestation that could operate in accordance with the present disclosure. Asshown, the example base station includes a wireless communicationinterface 48, a network communication interface 50, and a controller 52,all of which may be communicatively linked together by a system bus,network, or other connection mechanism 54.

In the context discussed above, this base station could be configured toengage in air-interface communication and to provide service accordingto a first RAT through the wireless communication interface 48. Further,the base station could be provided in a wireless communication systemthat includes a second base station that is configured to provideservice according to a second RAT. As noted above, these base stationsmay be collocated.

In this example base station, the wireless communication interface 48could comprise an antenna structure, which could be tower mounted orcould take other forms, and associated components such as a poweramplifier and a wireless transceiver, so as to facilitate providing acoverage area defining an air interface having a downlink and an uplink,and engaging in transmission and reception of user-plane data andcontrol-plane signaling over the air interface in accordance with thefirst RAT. And the network communication interface 50 could comprise awired or wireless interface, such as an Ethernet network communicationinterface, configured to support communication with other entities, suchas with the other base station and various core-network entities.

Further, controller 52 could comprise a processing unit (e.g., one ormore general purpose processors and/or specialized processors)programmed to cause the base station to carry out various operationssuch as those discussed above. For instance, the controller couldcomprise non-transitory data storage (e.g., one or more magnetic,optical, or flash storage components) holding program instructionsexecutable by the processing unit to cause the base station to carry outsuch operations.

In an example implementation, these operations could include (a)determining a buffer occupancy of the second base station, (b) using thedetermined buffer occupancy of the second base station as a basis tomake a decision of whether to configure for the UE dual-connectivityservice in which the UE is served concurrently over the first connectionwith the first base station according to the first RAT and over a secondconnection with the second base station according the second RAT, and(c) controlling configuration of the dual-connectivity service for theUE in accordance with the decision.

Various features discussed above could be implemented in this context aswell, and vice versa.

Exemplary embodiments have been described above. Those skilled in theart will understand, however, that changes and modifications may be madeto these embodiments without departing from the true scope and spirit ofthe invention.

We claim:
 1. A method for controlling configuration of dual-connectivityservice for a user equipment device (UE), wherein the dual-connectivityservice comprises the UE being served concurrently over a firstconnection according to a first radio access technology (RAT) and over asecond connection according to a second RAT, the method comprising:determining, by a first base station with which the UE has the firstconnection according to the first RAT, a buffer occupancy of a candidatesecond base station; using, by the first base station, the determinedbuffer occupancy of the candidate second base station as a basis to makea decision of whether to configure the dual-connectivity service withthe UE having the second connection with the candidate second basestation, wherein configuring the dual-connectivity service with the UEhaving the second connection with the second base station comprisescoordinating establishment for the UE of the second connection with thecandidate second base station; and controlling, by the first basestation, configuration of the dual-connectivity service for the UE inaccordance with the decision.
 2. The method of claim 1, wherein thebuffer occupancy comprises a measure based on at least one of downlinkbuffer occupancy and uplink buffer occupancy.
 3. The method of claim 2,wherein the downlink buffer occupancy is based on user-plane databuffered by the second base station pending transmission to one or moreUEs connected with the second base station.
 4. The method of claim 2,wherein the uplink buffer occupancy is based on user-plane data bufferedby one or more UEs connected with the second base station pendingtransmission to the second base station.
 5. The method of claim 1,wherein determining the buffer occupancy of the candidate second basestation comprises receiving from the candidate second base station areport of the buffer occupancy.
 6. The method of claim 1, wherein usingthe determined buffer occupancy of the candidate second base station asa basis to make the decision of whether to configure thedual-connectivity service with the UE having the second connection withthe candidate second base station comprises: making a determination ofwhether the determined buffer occupancy of the candidate second basestation is at least predefined threshold high; if the determination isthat the determined buffer occupancy of the candidate second basestation is at least predefined threshold high, then, based at least onthe determination, deciding to not configure the dual-connectivityservice with the UE having the second connection with the candidatesecond base station; and if the determination is that the determinedbuffer occupancy of the candidate second base station is not at leastpredefined threshold high, then, based at least on the determination,deciding to configure the dual-connectivity service with the UE havingthe second connection with the candidate second base station.
 7. Themethod of claim 1, wherein using the determined buffer occupancy of thecandidate second base station as a basis to make the decision of whetherto configure the dual-connectivity service with the UE having the secondconnection with the candidate second base station comprises: making adetermination of whether the determined buffer occupancy of thecandidate second base station is greater than a determined bufferoccupancy of another candidate base station; if the determination isthat the determined buffer occupancy of the candidate second basestation is greater than the determined buffer occupancy of anothercandidate base station, then, based at least on the determination,deciding to not configure the dual-connectivity service with the UEhaving the second connection with the candidate second base station; andif the determination is that the determined buffer occupancy of thecandidate second base station is not greater than the determined bufferoccupancy of the other candidate base station, then, based at least onthe determination, deciding to configure the dual-connectivity servicewith the UE having the second connection with the candidate second basestation.
 8. The method of claim 7, further comprising: if thedetermination is that the determined buffer occupancy of the candidatesecond base station is greater than the determined buffer occupancy ofthe other candidate base station, then, based at least on thedetermination, configuring the dual-connectivity service with the UEhaving the second connection with the other candidate base station. 9.The method of claim 1, wherein controlling configuration of thedual-connectivity service for the UE in accordance with the decisioncomprises: if the decision is to configure the dual-connectivity servicewith the UE having the second connection with the candidate second basestation, then engaging by the first base station in signaling toconfigure the dual-connectivity service with the UE having the secondconnection with the candidate second base station; and if the decisionis to not configure the dual-connectivity service with the UE having thesecond connection with the candidate second base station, then notengaging by the first base station in the signaling to configure thedual-connectivity service with the UE having the second connection withthe candidate second base station.
 10. The method of claim 1, whereinthe first RAT is 4G LTE, wherein the second RAT is 5G NR, and whereinthe dual-connectivity service is EN-DC.
 11. A method for controllingconfiguration of dual-connectivity service for a user equipment device(UE), wherein the dual-connectivity service comprises the UE beingserved concurrently over a first connection according to a first radioaccess technology (RAT) and over a second connection according to asecond RAT, the method comprising, while the UE has the first connectionwith a first base station: determining a buffer occupancy of a candidatesecond base station; using the determined buffer occupancy of thecandidate second base station as a basis to make a decision of whetherto configure the dual-connectivity service with the UE having the secondconnection with the candidate second base station, wherein configuringthe dual-connectivity service with the UE having the second connectionwith the second base station comprises coordinating establishment forthe UE of the second connection with the candidate second base station;and controlling configuration of the dual-connectivity service for theUE in accordance with the decision.
 12. In a wireless communicationsystem comprising a first base station configured to provide serviceaccording to a first radio access technology (RAT) and a second basestation configured to provide service according to a second RAT, thefirst base station comprising: a wireless communication interfacethrough which to engage in air-interface communication and provide theservice according to the first RAT; a controller, wherein the controlleris configured to carry out operations when a user equipment device (UE)is has a first connection with the first base station according to thefirst RAT, the operations including: determining a buffer occupancy ofthe second base station, using the determined buffer occupancy of thesecond base station as a basis to make a decision of whether toconfigure for the UE dual-connectivity service in which the UE is servedconcurrently over the first connection with the first base stationaccording to the first RAT and over a second connection with the secondbase station according the second RAT, wherein configuring thedual-connectivity service includes coordinating establishment of thesecond connection, and controlling configuration of thedual-connectivity service for the UE in accordance with the decision.13. The system of claim 12, wherein the buffer occupancy comprises ameasure based on at least one of downlink buffer occupancy and uplinkbuffer occupancy.
 14. The system of claim 13, wherein the downlinkbuffer occupancy is based on user-plane data buffered by the second basestation pending transmission to one or more UEs connected with thesecond base station.
 15. The system of claim 13, wherein the uplinkbuffer occupancy is based on user-plane data buffered by one or more UEsconnected with the second base station pending transmission to thesecond base station.
 16. The system of claim 12, wherein determining thebuffer occupancy of the second base station comprises receiving from thesecond base station a report of the buffer occupancy.
 17. The system ofclaim 12, wherein using the determined buffer occupancy of the secondbase station as a basis to make the decision of whether to configure forthe UE the dual-connectivity service in which the UE is servedconcurrently over the first connection with the first base stationaccording to the first RAT and over the second connection with thesecond base station according the second RAT comprises: making adetermination of whether the determined buffer occupancy of the secondbase station is at least predefined threshold high; if the determinationis that the determined buffer occupancy of the second base station is atleast predefined threshold high, then, based at least on thedetermination, deciding to not configure the dual-connectivity servicefor the UE in which the UE is served concurrently over the firstconnection with the first base station according to the first RAT andover the second connection with the second base station according thesecond RAT; and if the determination is that the determined bufferoccupancy of the second base station is not at least predefinedthreshold high, then, based at least on the determination, deciding toconfigure the dual-connectivity service for the UE in which the UE isserved concurrently over the first connection with the first basestation according to the first RAT and over the second connection withthe second base station according the second RAT.
 18. The system ofclaim 12, wherein using the determined buffer occupancy of the secondbase station as a basis to make the decision of whether to configure forthe UE the dual-connectivity service in which the UE is servedconcurrently over the first connection with the first base stationaccording to the first RAT and over the second connection with thesecond base station according the second RAT comprises: making adetermination of whether the determined buffer occupancy of the secondbase station is greater than a determined buffer occupancy of anotherbase station; if the determination is that the determined bufferoccupancy of the second base station is greater than the determinedbuffer occupancy of the other base station, then, based at least on thedetermination, deciding to not configure the dual-connectivity servicefor the UE in which the UE is served concurrently over the firstconnection with the first base station according to the first RAT andover the second connection with the second base station according thesecond RAT; and if the determination is that the determined bufferoccupancy of the second base station is not greater than the determinedbuffer occupancy of the other base station, then, based at least on thedetermination, deciding to configure the dual-connectivity service forthe UE in which the UE is served concurrently over the first connectionwith the first base station according to the first RAT and over thesecond connection with the second base station according the second RAT.19. The system of claim 18, wherein the operations further include: ifthe determination is that the determined buffer occupancy of the secondbase station is greater than the determined buffer occupancy of theother base station, then, based at least on the determination,configuring dual-connectivity service with the UE having the secondconnection with the other base station.
 20. The system of claim 12,wherein controlling configuration of the dual-connectivity service forthe UE in accordance with the decision comprises: if the decision is toconfigure the dual-connectivity service with the UE having the secondconnection with the second base station, then engaging by the first basestation in signaling to configure the dual-connectivity service for theUE; and if the decision is to not configure the dual-connectivityservice with the UE having the second connection with the second basestation, then not engaging by the first base station in the signaling toconfigure the dual-connectivity service for the UE.